The Arctic Climate Impact Assessment II

December 5th, 2004 by gavin

Another apparent ‘refutation’ appears in a CNS news story (a right-wing internet news service). The piece is predominantly an interview with Pat Michaels and other less prominent skeptics. We take their scientific points one at a time:

Michaels refuted McCain’s assertions about the North Pole, noting that the Arctic has actually been warmer in the past than it is now.

“It was warmer 4 to 7,000 years ago [in the Arctic.] Every climatologist knows that. I saw no mention of that in the Arctic report that was paraded in front of McCain,” Michaels said. He added that the past warming of the Arctic couldn’t possibly be blamed on greenhouse gas emissions since it occurred long before the industrial era.

This is a non-sequitur. The Arctic was warmer in the past but as a function of the change in the Earth’s orbit, something that isn’t relevant for explaining the current warming. 6000 years ago, changes in the Earth’s tilt and precession meant that the increase in high latitude solar radiation was around 5 W/m2 in the annual mean, and up to five times as much in the summer. This annual change is close to that projected for 2xCO2 later this century.

Next, Sallie Baliunas:

“Antarctica has been cooling for the last 50 years. Most of the Arctic has not warmed over long time scales,” Baliunas told CNSNews.com. Baliunas also serves as the enviro-science editor for Tech Central Station.

“Temperatures [have] always changed in the past and [they] always will. It can either go up or it goes down. We don’t have enough understanding of natural variability and we don’t see enormous amounts of temperature change to be alarmed about,” Baliunas explained.

The first point was addressed in a previous post, and the second statement probably refers to the mid-Holocene and so the previous comment on Michaels is relevant. The degree of natural variability is of course key in attributing climate change to anthropogenic changes, and all estimates of this based on proxy records in the past and modelling studies point to the recent warming as being outside the range of natural variability. Change is indeed a constant, but it is the magnitude and rate of change in the current situation that is unusual.

And finally, a new definition of the word ‘refute’:

McCain’s claims about a robin population explosion in the Arctic were refuted as well.

Marlo Lewis, a senior fellow at the Competitive Enterprise Institute (CEI), said “Even if it’s true that robins are making their first appearance in Arctic areas, what it means it that the robin’s habitat is expanding.”